Broadcasting without a bang (#497)

docs/src/reference/collective.md

@@ -11,6 +11,7 @@ MPI.Ibarrier
 
 ```@docs
 MPI.Bcast!
+MPI.Bcast
 MPI.bcast
 ```
 

src/collective.jl

@@ -60,6 +60,19 @@ function Bcast!(data, root::Integer, comm::Comm)
     Bcast!(Buffer(data), root, comm)
 end
 
+"""
+    Bcast(obj, root::Integer, comm::Comm)
+
+Broadcast the `obj` from `root` to all processes in `comm`. Returns the object.
+Currently `obj` must be `isbits`, i.e. `isbitstype(typeof(obj)) == true`.
+"""
+function Bcast(obj::T, root::Integer, comm::Comm) where T
+    if !isbitstype(T)
+        throw(ArgumentError("Bcast currently only supports `isbitstype`s."))
+    end
+    Bcast!(Ref(obj), root, comm)[]
+end
+
 """
     bcast(obj, comm::Comm; root::Integer=0)
 

test/test_bcast.jl

@@ -26,6 +26,29 @@ MPI.Bcast!(B, comm; root=root)
 @test B == A
 
 
+# Bcast: number
+A = 1.23
+B = MPI.Comm_rank(comm) == root ? 1.23 : 0.0
+res = MPI.Bcast(B, root, comm)
+@test typeof(res) == typeof(A)
+@test res == A
+
+# Bcast: scalar struct
+struct XY
+    x::Float64
+    y::Float32
+end
+A = XY(1.23, 4.56f0)
+B = MPI.Comm_rank(comm) == root ? A : XY(0.0, 0.0f0)
+res = MPI.Bcast(B, root, comm)
+@test typeof(res) == typeof(A)
+@test res == A
+
+# Bcast: array
+A = rand(3)
+B = MPI.Comm_rank(comm) == root ? A : zeros(3)
+@test_throws ArgumentError MPI.Bcast(B, root, comm)
+
 g = x -> x^2 + 2x - 1
 if MPI.Comm_rank(comm) == root
     f = g